The present invention concerns a tire or equivalent system, intended for fitting on heavy equipment of the heavy-vehicle, agricultural, or construction machinery type, the said tire comprising at least one carcass reinforcement surmounted radially by a tread.
Such tires consist of a carcass reinforcement usually surmounted radially by a crown reinforcement, itself covered radially by a tread, the said tread being connected to two tire beads by means of two sidewalls.
It is found that the use of such vehicles, particularly in the case of agricultural applications, leads to the crushing of crops. Contact between the vehicle and the ground takes place via the tire's contact area with the soil; the pressure exerted by the load and the tangential forces that result from the transmission of the braking and drive torques and lateral forces related to the dynamics of the vehicle can in effect damage the soil by compacting it, ploughing it up, or friction.
What users now want is to reduce the risk of damaging crops during use on farmlands due to the crushing of the crops as the vehicle, and more specifically its tires, pass over them.
To reduce soil crushing, it is known to reduce the pressure of the tires and/or increase their dimensions so as to reduce the pressure against the ground and therefore the crushing. In this way ground pressures lower than 1 bar can be obtained.
At this pressure level the structural rigidity of the tire is no longer negligible compared with its pneumatic rigidity, and because of this the distribution of pressures on the ground is not uniform; the shoulders of the tire carry more than its tread. This phenomenon of non-homogeneous pressure distribution over the contact area is accentuated if the ground has surface irregularities.
Until now, the numerous investigations by the applicant relating to modifications of meridian profiles of the tread, meridian profiles of the carcass reinforcement, materials for the carcass reinforcement and the crown, or modifications of the design and size of tread pattern blocks, have not brought the improvements hoped for.
It is also known to use paired tires, which can enable the crushing to be limited by reducing the pressure of each tire while preserving the load capacity. Such solutions, however, lead in particular to problems of bulkiness.
It is also known to use caterpillar tracks, which enable the average pressure exerted on the ground by the vehicle to be reduced still further.
Solutions of this type can allow the load to be distributed over a larger contact area and so to reduce the pressure exerted on the ground. In contrast, in the case of ground that has surface irregularities such that contact can only take place at a few high-points, an ordinary tire or caterpillar track leads to local excess pressures because of the said points.
A purpose of the invention is thus to provide tires or equivalent systems for heavy equipment which, in particular, cause less damage to the ground, particularly due to compacting or crushing as the equipment passes over it, whatever the nature of the ground and especially in the case of loose soil or ground with surface irregularities.